Probe Of Electron Correlation Research Articles

Towards high-resolution X-ray scattering as a probe of electron correlation.

X-ray scattering cross sections are calculated using a range of increasingly correlated methods: Hartree-Fock (HF), complete active space self-consistent field (CASSCF), Monte Carlo configuration interaction (MCCI), and full configuration interaction (FCI). Even for the seemingly straightforward case of ground state Ne, the accuracy of the total scattering is significantly better with a more correlated wavefunction. Scanning the bond distance in ground state CO shows that the total scattering signal tracks the multireference character. We examine the convergence of the elastic, inelastic, and total scattering of O3. Overall, the inelastic and total components are found to be the most sensitive to the strength of correlation. Our results suggest that highly accurate measurement of X-ray scattering could provide a sensitive probe of pair-wise correlation between electrons.

The probe of electron correlation along the He isoelectronic sequence by intense and short laser pulses

The two-photon double ionization process along the He isoelectronic sequence (He − Ne8+) is investigated by solving the full-dimensional time-dependent Schrödinger equation in an intense laser field. The ionization is triggered from the ground state of each system with photons of energy higher than its second ionization potential, in which case the sequential two-electron ejection is allowed. The results of the total two-photon double ionization probability and the energy distribution of ejected electrons demonstrate the important effect of the nuclear charge Z on the dynamics of the interaction between the two ejected electrons.

Proposed Alteration of Images of Molecular Orbitals Obtained Using a Scanning Tunneling Microscope as a Probe of Electron Correlation

Scanning tunneling spectroscopy (STS) allows us to image single molecules decoupled from the supporting substrate. The obtained images are routinely interpreted as the square moduli of molecular orbitals, dressed by the mean-field electron-electron interaction. Here we demonstrate that the effect of electron correlation beyond the mean field qualitatively alters the uncorrelated STS images. Our evidence is based on the ab initio many-body calculation of STS images of planar molecules with metal centers. We find that many-body correlations alter significantly the image spectral weight close to the metal center of the molecules. This change is large enough to be accessed experimentally, surviving to molecule-substrate interactions.

Superconducting Probe of Electronic Correlations and Exchange Field Based on the Proximity Effect in F/S Nanostructures

The proximity effect and competition between the BCS and LOFF states are studied in the Cooper limit for thin F/S and F/S/F nanostructures, where F is a ferromagnet and S is a superconductor. The dependences of the critical temperature Tc on the exchange field I, electron correlations λf, and the thickness df of the F layer are derived for F/S bilayers and F/S/F trilayers. Two new π-phase superconducting states with electronelectron repulsion in the F layers of F/S/F trilayers are predicted. A 2D LOFF state in F/S/F trilayers is possible only in the presence of a weak magnetic field and the appropriate parameters of the F and S layers. The absence of the suppression of 3D superconductivity in short-period Gd/La superlattices is explained and the electronelectron coupling constant in gadolinium is predicted. A method of superconducting probe spectroscopy based on the proximity effect is proposed for determining the symmetry of the order parameter, the magnitude and sign of electron correlations, and the exchange field in various nanomagnets F.

Superconducting probe of electronic correlations and exchange field based on the proximity effect in F/S nanostructures

The proximity effect and competition between the BCS and LOFF states are studied in the Cooper limit for thin F/S and F/S/F nanostructures, where F is a ferromagnet and S is a superconductor. The dependences of the critical temperature on the exchange field I, electron correlations λf, and the thickness df of the F layer are derived for F/S bilayers and F/S/F trilayers. In addition, two new π-phase superconducting states with electron-electron repulsion in the F layers of F/S/F trilayers are predicted. A two-dimensional LOFF state in F/S/F trilayers is possible only in the presence of a weak magnetic field and the appropriate parameters of the F and S layers. The absence of the suppression of three-dimensional superconductivity in short-period Gd/La superlattices is explained and the electron-electron coupling constant in gadolinium is predicted. A method of superconducting sounding spectroscopy based on the proximity effect is proposed for determining the symmetry of the order parameter, the magnitude and sign of electron correlations, and the exchange field in various nanomagnets F.

Proximity Effect as a Probe of Electronic Correlations and Exchange Field in Dirty Ferromagnet/Superconductor Nanostructures

We investigate the interplay between the BCS and 2D Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) states in the dirty thin ferromagnetic metal/superconductor (FM/S) nanostructures. For the FM/S bilayers we have derived the dependencies of critical temperature on the FM layer exchange field, electronic correlations and thickness. Moreover, in the corresponding FM/S/FM trilayers we predict two new π phase superconducting states with electron-electron repulsion in the FM layers. The 2D modulated LOFF states are possible in such trilayers only in presence of a weak magnetic field and at suitable parameters of the FM and S layers. On this base we originally propose the method of proximity effect probe the magnitude and sign of the electronic correlations, the order parameter symmetry and exchange fields in various FM layers.

The Utilization of Spin Polarized Photoelectron Spectroscopy as a Probe of Electron Correlation with an Ultimate Goal of Pu

AbstractWe are developing the technique of spin-polarized photoelectron spectroscopy as a probe of electron correlation with the ultimate goal of resolving the Pu electronic structure controversy. Over the last several years, we have demonstrated the utility of spin polarized photoelectron spectroscopy for determining the fine details of the electronic structure in complex systems such as those shown below.

Facilities for the Performance of Fano Effect Measurements as a Probe of Electron Correlation

AbstractFano Effect measurements are the key to direct observation of the Kondo or spin shielding intrinsic to models of electron correlation. The Fano Effect is the observation of spin polarized photoelectron emission from NONMAGNETIC materials, under chirally selective excitation, such as circularly polarized photons. Below are described three spectrometers, with which Fano Effects measurements have been made.

Inelastic x-ray scattering as a probe of electronic correlations

We construct an exact dynamical mean field theory for nonresonant inelastic light scattering in the infinite-dimensional Falicov-Kimball model, which can be tuned through a quantum critical metal-insulator transition. Due to the projection of the polarization orientations onto different regions of the Brillouin zone and due to the transfer of energy and momentum from the light to the strongly correlated charge excitations, the nature of the dynamics can be naturally interpreted as strongly temperature-dependent low-energy particle-hole excitations and weakly temperature-dependent high-energy charge transfer excitations which depend delicately on the electronic correlations. These results can be used to give important information concerning the evolution of charge dynamics in different regions of the Brillouin zone.

Donor Impurities as a Probe of Electron Correlations in a Two-Dimensional Electron Gas in High Magnetic Fields

Many-electron effects have been observed in far-infrared magnetospectroscopic studies of GaAs/AlGaAs multiple quantum wells (QWs), $\ensuremath{\delta}$ doped with Si donors in both well and barrier centers. With increasing excess electron densities in the QWs the negative donor ion $({D}^{\ensuremath{-}})$ singlet and triplet transitions are substantially blueshifted, exhibiting cusps at integer and fractional filling factors. At high magnetic fields the many-electron system appears to approach a collection of isolated two-electron ${D}^{\ensuremath{-}}$ ions. Exact diagonalization studies of donor and confined electrons show the importance of electron correlations and localization at high magnetic fields in understanding this behavior.

Low Energy Auger Electrons - a Probe of Electron Correlations in Atoms and Molecules

Until very recently Auger decay was exclusively regarded as an inner-shell phenomenon. However, recent studies of the decay of certain valence states in atoms and molecules excited by electron correlation accompanying photoinization have shown the importance of non-radiative decay processes, so-called particular Auger transitions. The fact that such states decay non-radiatively was previously ignored, and is of critical importance for the interpretation of double-photoinization data, for both, photoion yield measurments, particularly near threshold, and photoelectron spectra, especially at low kinetic energies. Hence the spectroscopy of these participator Auger transitions is of considerable interest for our understanding of electron correlations. Two modes of such transitions were identified; the inner-valence type in which the inner vs hole is filled in the decay process, and the valence-multiplet type in which the valence shell remains unchanged in occupancy during the transition, but experiences a change of LS multiplet symmetry. The analysis of these processes shows that in the sudden limit up to 30-40% of the double-ionization rate in neon and argon is due to particular Auger decay, which was previously attributed to simultaneous double ionization.

Nuclear relaxation in organic conductors as a probe of electronic correlations

In this paper we are making use of the extended scaling hypothesis for an NMR analysis of electronic correlations in organic conductors. We derive the general dynamical scaling form of the nuclear relaxation rate T 1 −1 for antiferromagnetic type of correlations in a quasi -1D conductor. The results are compared to existing T 1 −1 data for the (TMTTF) 2X and (TMTSF) 2X series of organic compounds giving a strong body of evidence for sizeable 1D collective effects precursors to all phase transitions observed.